Generally, this type of binding processing apparatus is known as an apparatus that performs binding processing on a bunch of sheets supported on a paper mount (sheet support section) as a post-processing apparatus in an image formation system, or the like. As a binding processing mechanism, known are a mechanism (staple binding mechanism) for binding a bunch of sheets with a staple, and a mechanism (press binding mechanism) for applying narrow pressure to a bunch of sheets with pressurizing surfaces having concavo-convex surfaces to perform press binding.
The press binding mechanism for performing binding processing on a bunch of sheets without using a metal needle is commonly used for a method of enabling bound sheets to be easily separated and divided and not affecting the environment in discarding documents. On the other hand, such a problem is also known that the sheet peels off when a bunch thickness of a bunch of sheets to perform binding processing is thick, page turning is performed vigorously or the like.
For example, Patent Document 1 discloses a press binding mechanism, and proposes the mechanism for increasing or decreasing a press binding region (press-binding area) corresponding to a bunch of sheets to perform binding processing. The Document discloses the mechanism that is a pressurizing mechanism in the shape of gears which rotate in a mutually meshing state in which by adjusting the rotation amount, strong binding is obtained when a band-shaped binding portion is long, and weak binding is obtained when the portion is short.
Further, in Patent Document 2, it is configured to enable strong binding or weak binding to be selected by changing the angle direction of a press binding pressurizing region. Then, in applying narrow pressure to sheets with a pair of pressurizing surfaces to perform press binding, the sheets are deformed in the shape of gathers. Binding easy to peel (weak binding) or binding hard to peel (strong binding) is selected by changing a mesh width (short-side direction) and mesh length (long-side direction) in the arrangement direction with respect to the sheet turning direction.